High Temperature Hydrogen Attack

High Temperature Hydrogen Attack degradation can build up to more extensive damage over time, risking costly shutdowns, slowing production, and creating a hazardous environment for plant personnel. When steel is exposed to atomic Hydrogen at high temperatures and pressures, hydrogen atoms may dissolve into methane, accumulating in bubbles that connect to create micro-fissures at steel grain boundaries. These micro fissures reduce the strength of the metal and cause cracks to form in the steel. cracking can cause complete asset failure for critical steel componentry such as welds, piping, and exchangers, catalytic equipment, and more.

Engineering Assessments

At TTIS Ventures Private Limited, our well qualified experts conduct unit-by-unit reviews of all equipment and piping materials that may be affected to ensure their operating conditions are in compliance with regulations and industry-best practices.

We also conduct GAP assessments of current mechanical integrity programs and inspection plans as they relate to detection and prevention, to determine if any adjustments are needed. Fitness-for-Service assessments assist operators in making run-repair-replace decisions.

After these assessments, TTIS develops inspection execution plans.

Inspection Services

TTIS Ventures Private Limited effective inspection plans result in:

  • Significant reduction of risk

  • Cost-efficient inspection procedures

  • Accurate, timely results allowing for immediate action and repair

  • Early detection of cracking

Hydrogen Induced Cracking (HIC)

Hydrogen Induced Cracking (HIC) is a common form of wet H2S cracking caused by the blistering of a metal due to a high concentration of hydrogen. The blistering damage tends to form parallel to the surface and to the direction of hoop stress.

HIC usually occurs due to the effects of aqueous hydrogen charging of steel in wet Hydrogen Sulphide (H2S) refinery process environments. It can occur at relatively low temperatures, largely as a result of atomic hydrogen from wet H2S corrosion reactions which enter the steel and collect at inclusions or impurities within the steel. The H2S prevents the hydrogen recombination reaction that would normally occur so, rather than bubbling off from the corroding surface, the hydrogen atoms are forced into the metal structure causing corrosion and weakness.

The damage occurs when the hydrogen collects at inclusions or impurities in the steel. It tends primarily occur in steels that have a hardness of 22 or more on the Rockwell C scale. It is manifested as blisters or blister cracks oriented parallel to the plate surface.

As far as damage mechanisms go HIC is not always dangerous. It usually isn’t damaging until it becomes extensive and begins to affect the material properties. Once the ductility of the metal has reduced to a significant amount, the metal will form stepwise internal cracks connecting adjacent hydrogen blisters. These can become dangerous should they propagate into a weld.

The inspection requires characterization of the defect areas to differentiate between spot inclusions, laminations, and different stages of hydrogen-induced cracking (HIC).

Type of Defects

  • Spot inclusions

  • Laminations

  • Side step cracking (SOHIC)


Carburization involves the absorption of carbon into steel or alloy during operation in a high temperature environment, typically above 593C. Carbon from the carborizing environment enters the surface of the steel by diffusion, causing the metal to become embrittled and lose creep resistance and toughness. The result is a loss of corrosion resistance and strength and an increased susceptibility to cracking type failures. Because it occurs in high temperature environments, carburization often affects furnace tubes. It typically occurs when furnace firing is increased to compensate for a heavy coke deposit on the ID of the tube. The increase in temperature and the coke adjacent to the tube wall can produce a highly carburizing environment, in which carbon can enter steel via diffusion.